Loudspeaker Excursion Control Using Time-Domain Admittance Modeling
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Solution Overview
Problem
Existing loudspeaker models are unreliable when there are discrepancies between expected and actual loudspeaker/enclosure characteristics due to manufacturing tolerances or mechanical damage, leading to inaccurate diaphragm displacement predictions.
Innovation Solution
A method that measures voltage and current over time to derive an admittance function, combines it with the force factor and blocked electrical impedance, and calculates the input-voltage-to-excursion transfer function, allowing for time-domain estimation and control of loudspeaker output without requiring prior knowledge of the enclosure type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If parametric models with fixed enclosure assumptions are used, then the model structure is simple and easy to implement, but the model becomes invalid when there are manufacturing tolerances or mechanical damage affecting the loudspeaker/enclosure characteristics
Solution Approach 1:
The patent transitions from static parametric models with fixed enclosure assumptions to dynamic non-parametric models that continuously adapt to changing loudspeaker characteristics. The system monitors electrical impedance changes over time and updates the model accordingly, allowing the model to remain valid despite manufacturing tolerances or mechanical damage.
Solution Approach 2:
The patent changes the modeling approach from using fixed physical parameters (enclosure type, volume, mass) to using time-varying electrical impedance measurements. By monitoring impedance changes and deriving transfer functions from these measurements, the model automatically adjusts to reflect actual loudspeaker conditions without requiring explicit knowledge of enclosure changes.
2Reliability
If time-domain estimation method is used, then the model remains valid with changes in loudspeaker or enclosure characteristics, but the computational complexity increases compared to frequency-domain approaches
Solution Approach 1:
The patent implements a feedback mechanism where electrical impedance measurements are continuously monitored and fed back into the model. The system uses these measurements to update the transfer function estimates in real-time, creating a self-adjusting model that maintains validity without requiring complex external calibration procedures.
Solution Approach 2:
The system performs self-characterization by using its own electrical impedance measurements to build and update its model. The loudspeaker system essentially models itself through the electrical measurements taken during normal operation, eliminating the need for external testing equipment or complex calibration procedures.
3Measurement precision
If complex parametric models are used to account for enclosure variations, then model accuracy improves, but the ease of manufacture and implementation decreases
Solution Approach 1:
The patent replaces complex mechanical modeling (enclosure types, volumes, masses) with electrical measurements and signal processing. By using electrical impedance measurements and deriving mechanical transfer functions from these electrical characteristics, the system achieves accurate displacement predictions without requiring complex mechanical models or physical measurements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a robust and adaptable model that remains valid even with changes in loudspeaker or enclosure characteristics, offering reliable loudspeaker protection and acoustic signal processing without the need for complex parametric models.
Implementation Method 1
a force factor of the loudspeaker... The voltage applied to a voice coil of the loudspeaker generates a Lorentz force in response
Data Source
AI summary
A method of controlling a loudspeaker output comprises deriving an admittance function over time from the voice coil voltage and current. In combination with a delta function, the force factor of the loudspeaker and the blocked electrical impedance, the input-voltage-to-excursion transfer function over time is obtained. This is used to control audio processing for the loudspeaker thereby to implement loudspeaker protection and/or acoustic signal processing; The invention provides a modelling and control approach which is not based on a parametric model. As a consequence, it does not require prior knowledge regarding the enclosure (e.g. closed or vented box) and can cope with complex designs of the enclosure.